In the field of vehicle construction, the development and implementation of lightweight materials or components is becoming more and more important in order to satisfy criteria for lightweight construction. The demand for weight reduction is especially driven by the goal of reduction of CO2 emissions. The growing concern for occupant safety also leads to the adoption of materials which improve the integrity of the vehicle during a crash while also improving the energy absorption.
A process known as Hot Forming Die Quenching (HFDQ) (also known as hot stamping or press hardening) uses boron steel sheets to create stamped components with Ultra High Strength Steel (UHSS) properties, with tensile strengths of e.g. 1.500 MPa or even up to 2000 MPa or more. The increase in strength as compared to other material allows for a thinner gauge material to be used, which results in weight savings over conventionally cold stamped mild steel components.
The steel sheets may be coated or uncoated. However, in order to improve corrosion protection, before, during or after a hot stamping process, coatings may be applied. For example the use of Al—Si coatings or Zn coatings is known.
Depending on the composition of the base steel material, blanks may need to be quenched (i.e. be cooled down rapidly) to achieve the high tensile strengths. Also examples of steel material which can harden at room temperature by air cooling with relatively low cooling speed are known.
The hot stamping process may be performed in a manner such that a blank to be hot formed is heated to a predetermined temperature e.g. austenization temperature by, for example, a furnace system so as to decrease the strength i.e. to facilitate the hot stamping process. The blank to be hot formed may be formed by, for example, a press system having a low temperature compared to the blank (e.g. room temperature) and a temperature control, thus a shaping process and a heat treatment using the temperature difference may be performed.
The use of multistep press systems for manufacturing hot formed elements is known. The multistep press systems may comprise a plurality of tools configured to perform different operations on blanks simultaneously. With such arrangements, a plurality of blanks undergo different manufacturing steps simultaneously during each stroke using the tools forming the multistep press systems, thus the performance of the system may be increased.
A multistep press system may include a conveyor or a transferring device which transfers the heated blank to a press tool which is configured to press the blank. Additionally, a furnace system that heats and softens the blank to be hot formed may be provided upstream from the multistep press system or apparatus. Furthermore, a separate laser process step or a separate cutting tool may also be provided, wherein the stamped blanks are discharged from the press system and are transferred and located into the laser process step or in the separate cutting tool in order to be manufactured e.g. cut and/or trimmed and/or pierced and/or punched.
Generally, in such systems, an external pre-cooling tool is used in order to previously cool down the blank to be hot formed. For example, zinc coated steel blanks need to be cooled down before a hot forming process to reduce or minimize problems such as microcracks. Once the blank is cooled down, it is transferred from the external pre-cooling tool to the multistep press apparatus or system.
The present disclosure seeks to provide improvements in multistep processes and systems.